1. Field of Invention
The invention relates to an apparatus driven by a pressurized medium. The apparatus is comprised of an actuator, which is articulately mounted to be swingable around a swing axis, a line segment, and a connecting element, which is connectable to the actuator. The invention further relates to a loading machine such as an agricultural, forestry machine, or a construction machine.
2. Related Technology
German Patent specification DE 14 81 066 discloses a pressurized-medium-driven apparatus, specifically a hydraulic apparatus employed for swinging, raising or lowering extension arms or front-end loaders on loader vehicles. Ordinarily, such hydraulic apparatuses have a hydraulic cylinder which is swingably mounted between the extension arm or swing arm assembly and a frame of the vehicle. When the hydraulic cylinder is expanded or contracted, the extension arm or swing arm assembly is raised or lowered. Typically, pressurized hydraulic fluid is supplied to the hydraulic cylinder via a rigid hydraulic line comprised of metal, which is connected to flexible hydraulic tubes comprised of plastic or rubber. The metal hydraulic lines are usually mounted on the swingable component parts and are fixed by a suitable holding means. The flexible hydraulic tubes are particularly used for connection between the supply line and the hydraulic cylinder because they are flexibly deformable. The flexible hydraulic tubes can accommodate the relative movements which occur between the hydraulic cylinder and the supply line during a swinging movement.
Flexible hydraulic tubes, when used, are susceptible to potential leakage, and cracking and bursting. Flexible tubes are less robust than metallic lines and thus are more susceptible to damage from articles and obstacles that can come into the range of movement of the hydraulic cylinder. Further, the materials used for flexible hydraulic tubes are more apt to crack or burst than the materials of rigid metal lines.
In the light of these risks, a safety means can be provided that provides protection in the event of failure of the flexible hydraulic tubes and to prevent a sudden loss of pressure in the hydraulic cylinder as a result of such failure. Parts of the hydraulic system that are exposed to the machine load, a loss in pressure would be accompanied by sudden lowering of the extension arm or swing arm assembly. To provide a protective means for the hydraulic cylinders against bursting tubes, loader vehicles, such as telescope loaders, are provided with safety valves, in the form of load-retaining valves, pressure-retaining valves, or tube break protectors, disposed in a part of the hydraulic system exposed to the machine load, namely between the flexible hydraulic tube and the inlet of the hydraulic cylinder. These safety valve arrangements can lead to disadvantageous limitations concerning the engineering design and compactness of the hydraulic system, because the safety valves must be mounted directly on the hydraulic cylinder or integrated into the cylinder housing.